This invention relates generally to devices for monitoring a difference between the speeds of two rotating members and more specifically to a system employing a gear differential disposed in a rotatable housing and connected between a vehicle wheel and an inertial vehicle speed reference, such as a flywheel, to monitor the occurence of a wheel skid or spin condition. The device also generates a fluid or other signal suitable for maintaining two rotating members at the same speed or for controlling a vehicle brake applicable to each wheel to control such skid or spin conditions.
Previously, I have disclosed a system for automatically controlling the brakes applicable to a vehicle wheel to control skidding or spinning thereof which provides a continual demand for fluid from a vehicle fluid supply source. See my previously filed U.S. Patent application, Ser. No. 640,865, filed Dec. 15, 1975, now U.S. Pat. No. 4,088,375 entitled, Automatic Skid and Spin Control System for Vehicle Brakes and Method. Also in order to maintain a constant low pressure supply of air or vacuum to that system, even when the vehicle brakes are not in use, additional valves are required. Further, in order to insure rapid response to a wheel spin condition, a by-pass valve must be employed to direct high pressure air directly from the fluid source to the fluid valve wheel and vehicle speed sensors and thereby by-pass certain valves operated by the brake pedal and responsive thereto. Also, a loss of fluid to a certain portion of that system through mechanical failure or rupture of a line could prevent manual brake application to the vehicle wheels.
The device of my invention, particularly when employed in a vehicle brake control system substantially overcomes these and other difficulties encountered in the prior art.